JP3219217B2 - Positioning method and apparatus, and exposure method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for sequentially transferring a reticle pattern image onto each shot area of a wafer based on, for example, array coordinates calculated by statistical processing. The present invention relates to a suitable alignment method applied to the case of alignment.

[0002]

2. Description of the Related Art When a semiconductor element or a liquid crystal display element is manufactured by a photolithography process, a photosensitive material is applied to a pattern image of a photomask or a reticle (hereinafter collectively referred to as a "reticle") via a projection optical system. A projection exposure apparatus for projecting each shot area on a wafer is used.
In recent years, as this type of projection exposure apparatus, a wafer is mounted on a two-dimensionally movable stage, and the wafer is moved (stepped) by this stage, and a pattern image of a reticle is transferred to each shot area on the wafer. A so-called step-and-repeat type exposure apparatus, in particular, a reduction projection type exposure apparatus (stepper) is frequently used.

[0003] For example, since a semiconductor element is formed by superposing a large number of circuit patterns on a wafer, when projecting and exposing the circuit patterns of the second and subsequent layers onto the wafer, the circuit pattern is already formed on the wafer. It is necessary to accurately align each shot area with the reticle pattern image, that is, the alignment (alignment) between the wafer and the reticle. A conventional method of aligning a wafer in a stepper or the like is roughly as follows (for example, see Japanese Unexamined Patent Publication No.
No. 44429).

That is, a plurality of shot areas (chip patterns) each including a positioning mark called a wafer mark are formed on a wafer, and these shot areas are arranged at predetermined coordinates on the wafer. Are arranged regularly based on However, even if the wafer is stepped on the basis of the designed arrangement coordinate values (shot arrangement) of a plurality of shot areas on the wafer, the wafer is not always accurately aligned due to the following factors.

(1) The residual rotation error θ of the wafer (2) The orthogonality error w of the stage coordinate system (or shot arrangement) w (3) The linear expansion / contraction (scaling) Rx, Ry of the wafer (4) The wafer (center position) Offset (translation) O
x, Oy

At this time, the coordinate transformation of the wafer based on these four error amounts (six parameters) can be described by a linear transformation equation. Therefore, for a wafer in which a plurality of shot areas including a wafer mark are regularly arranged, the coordinate system (x, y) on the wafer is converted into a coordinate system (X, Y) on the stage as a stationary coordinate system. Can be expressed as follows using the six conversion parameters a to f.

[0007]

(Equation 1)

The six conversion parameters a to f in this conversion equation can be obtained, for example, by the least squares approximation method. In this case, the design coordinates on the coordinate system (x, y) associated with each of several shot areas selected from a plurality of shot areas (chip patterns) on the wafer are (x1, y1). , (X2, y2), ‥‥, (x
(n, yn) to a predetermined reference position (alignment). Then, the coordinate value (xM) in the coordinate system (X, Y) on the stage at that time.
1, yM1), (xM2, yM2), ‥‥, (xMn,
yMn) is actually measured.

The calculated array coordinates obtained by substituting the designed array coordinates (xi, yi) (i = 1, ウ エ ハ, n) of the selected wafer mark into the above-described primary conversion model. (Xi, Yi) and the coordinates (x
The difference (△ x, △ y) from (Mi, yMi) is considered as an alignment error. The one alignment error Δx is represented by, for example, the sum of (Xi−xMi) ² with respect to i, and the other alignment error Δy is represented by, for example, the sum of (Yi−yMi) ² with respect to i.

Then, the alignment errors △ x and △ y are partially differentiated sequentially with six conversion parameters a to f, an equation is set such that the value becomes 0, and the six simultaneous equations are solved. For example, six conversion parameters a to f are obtained. Thereafter, the alignment of each shot area of the wafer can be performed based on the array coordinates calculated using the primary conversion formulas using the conversion parameters a to f as coefficients.
Alternatively, when the approximation accuracy is not good in the linear conversion formula, the wafer may be aligned using, for example, a quadratic or higher-order formula.

[0011]

In the prior art as described above, there is one value on the stage coordinate system for each wafer mark belonging to the shot area selected for obtaining the conversion parameter. However, in general, the position of each wafer mark is obtained by performing a predetermined process on a measurement signal obtained by photoelectrically converting light obtained by irradiating each wafer mark with alignment light, The actual measured values of the wafer marks on the stage coordinate system differ depending on signal processing conditions such as a threshold level.

For example, when a measurement signal obtained from a wafer mark changes in a chevron shape in the measurement direction, an intermediate point between two intersections obtained by slicing the measurement signal at a certain threshold (slice level) is determined. A method of setting the position of the wafer mark can be considered. However, in this method, if the measurement signal is not symmetric in the measurement direction, the position of the obtained wafer mark differs depending on the set threshold. Therefore, when the conversion parameter is obtained by the least square method, the value of the conversion parameter to be obtained differs depending on which value is used as the actually measured position of each wafer mark. Therefore, what kind of signal processing condition finally determines the position of the wafer mark to be used is a problem. Conventionally, the signal processing condition is determined for each process by trial and error, for example.

In view of the above, the present invention provides a statistical processing based on a result obtained by actually measuring the positions of alignment marks belonging to a selected shot area on a wafer to be processed in advance. In the alignment method of obtaining the conversion parameters according to the above and calculating the alignment coordinates of each shot area on the wafer based on the calculated array coordinates calculated using the conversion parameters, from the alignment marks actually measured, It is an object of the present invention to automatically optimize signal processing conditions of an obtained measurement signal.

[0014]

Alignment method according to the invention According to an aspect of, for example, as shown in FIGS. 1 and 5, a preset of
Each of the plurality of processing regions (ESi) regularly arranged on the substrate (W) according to the obtained arrangement information is converted into a predetermined position in a stationary coordinate system (X, Y) for defining the movement position of the substrate (W). in registering sequential position relative to the working position, the plurality of the processing region (ESi), preselected at least three stationary coordinate system of the processing region (SA1~SA3) (X, Y) position on measured information, by statistical calculations these measured plurality of positional information have been, each stationary coordinate system of the substrate (W) a plurality of the processed region on the (ESi) (X, Y) of the sequence information on the By calculating and controlling the movement position of the substrate (W) according to the calculated arrangement information of each of the plurality of processed regions ( ESi ), each of the plurality of processed regions (ESi) is Align to machining position It relates to a method for.

Further, according to the present invention, when measuring the position information of at least three pre-selected processing areas (SA1 to SA3) on the stationary coordinate system (X, Y), the measurement target of the processing areas is determined. The measurement signal obtained from the object (positioning mark) is processed under the first signal processing condition,
Position information, and based on the first position information,
From the preset array information of the array on its stationary coordinate system
Determining a set of first conversion parameters for calculating information;
(Steps 103 and 104), the measurement signal is
Processed under a second signal processing condition different from the first signal processing condition
To obtain the second position information, and based on the second position information,
From the preset array information on the stationary coordinate system.
Set of second conversion parameters for calculating sequence information of
(Steps 107, 108, 103, 104)
Of the multiple sets of conversion parameters obtained in that way,
Select one set of conversion parameters based on predetermined conditions
Then, using the selected set of conversion parameters, the arrangement information on the stationary coordinate system (X, Y) of each of the plurality of processing regions (ESi) on the substrate (W) is calculated. (Step 111). In this case,
The fixed condition is, for example, for each set of conversion parameters,
The static coordinate system calculated using this transformation parameter
Is measured under the above location information and its signal processing conditions.
Including the residual error component with the
Select the set of transformation parameters when is minimum
Is desirable. Also, the exposure method of the present invention
On the substrate, calculated using the alignment method
Array information on its stationary coordinate system for each of the
A predetermined pattern is formed on a substrate that has been aligned using
It is to be transcribed. Also, the positioning device of the present invention
Are regularly arranged on the board according to the preset sequence information.
Move each of the arrayed processing areas to the substrate
For a given machining position in the stationary coordinate system that defines the position
When sequentially aligning, the plurality of processing areas
Of at least three pre-selected work areas,
Position information on the stationary coordinate system of
Statistical calculation of multiple location information
In each of the plurality of work areas on the plate in its stationary coordinate system
Array information is calculated, and the plurality of
Each sequence information Engineering area thus the movement position of the substrate
By controlling, each of the plurality of processing regions
In a device that aligns with the processing position,
Of at least three pre-selected work areas
When measuring position information on a stationary coordinate system,
Signal processing strip of measurement signal obtained from the measurement object in the work area
The position of the area to be machined
Measurement means for measuring information and the signal
The position information measured for each processing condition and its preset
Based on the set sequence information and the preset sequence
To calculate the array information on the stationary coordinate system from the information
One set of conversion parameters is calculated for each signal processing condition.
First calculating means, and a plurality of sets of calculated conversion parameters.
One of the conversion parameters among the data
Means for selecting based on the
Using the conversion parameters, multiple processing areas on the substrate
Computes array information for each of the regions on its stationary coordinate system
And second operation means. In addition, the present invention
Exposure apparatus is calculated by the alignment apparatus of the present invention.
The rest of each of the plurality of processing areas on the substrate
Substrate aligned using coordinate information on the coordinate system
A predetermined pattern is transferred thereon.

[0016]

According to the present invention, for example, on a substrate (W)
Using the set coordinate system as a sample coordinate system (x, y), at least three pre-selected work areas (SA1 to SA1)
When measuring the coordinate position on the stationary coordinate system (X, Y) in 3), the measurement object in the processed area is used as a positioning mark. If the midpoint between two intersections obtained by slicing the measurement signal obtained from the alignment mark at a predetermined threshold level is regarded as the coordinate position of the alignment mark, for example, the signal An example of the processing condition is the threshold level. Therefore, the coordinate position of the alignment mark is obtained by changing the threshold level in various ways, and a plurality of processing regions (ES
A set of conversion parameters for calculating the array coordinates on the stationary coordinate system (X, Y) is obtained from the array coordinates on the sample coordinate system (x, y) in (i).

Thereafter, the obtained plural sets of conversion parameters
One of the conversion parameters of the
And a plurality of processing regions (ESi) on the substrate (W) using the selected set of conversion parameters.
Each of the stationary coordinate system (X, Y) of calculating the sequence information on. As a result, in the present invention, the signal processing conditions are automatically set.
Can be optimized. In particular, the set of conversion parameters
For each meter, on the calculated stationary coordinate system (X, Y)
Array coordinates and coordinates measured under the signal processing conditions
A residual error component from the position is obtained (step 105).
The set of conversion parameters when the residual error component is minimized
Using the data, a plurality of processing regions (ES) on the substrate (W)
array coordinates on each stationary coordinate system (X, Y) of i)
Is calculated (step 111) , the conditions for optimizing the signal processing conditions such as the threshold level are as follows:
The condition is to minimize the residual error component. By minimizing the residual error component in this way, the positioning accuracy is further improved.

[0018]

1 to 8 show a first embodiment of the present invention .
This will be described with reference to FIG. FIG. 2 shows a schematic configuration of a projection exposure apparatus suitable for applying the alignment method of this embodiment. In FIG. 2, the illumination light IL generated from the extra-high pressure mercury lamp 1 is reflected by the elliptical mirror 2. After being condensed once at the second focal point, the light enters the illumination optical system 3 including a collimator lens, an interference filter, an optical integrator (fly-eye lens), an aperture stop (σ stop), and the like. Although not shown, the fly-eye lens is arranged in an in-plane direction perpendicular to the optical axis AX such that its reticle-side focal plane substantially matches the Fourier transform plane (pupil conjugate plane) of the reticle pattern.

A shutter (for example, a rotary shutter with four blades) 37 for closing and opening the optical path of the illumination light IL by a motor 38 is arranged near the second focal point of the elliptical mirror 2. In addition, as the illumination light for exposure, in addition to the bright line of the ultrahigh-pressure mercury lamp 1 or the like, a laser beam such as an excimer laser (KrF excimer laser, ArF excimer laser, or the like), or a harmonic of a metal vapor laser or a YAG laser is used. It does not matter.

In FIG. 2, illumination light (i-line or the like) IL in a wavelength region for exposing the resist layer emitted from the illumination optical system 3 to light.
Is reflected by the beam splitter 4, passes through a first relay lens 5, a variable field stop (reticle blind) 6 and a second relay lens 7, and passes through a mirror 8.
Leads to. Then, the illumination light IL reflected substantially vertically downward by the mirror 8 illuminates the pattern area PA of the reticle R with a substantially uniform illuminance via the main condenser lens 9. The arrangement surface of the reticle blind 6 has a conjugate relationship (image formation relationship) with the pattern formation surface of the reticle R, and the drive system 36
By opening and closing a plurality of movable blades constituting the reticle blind 6 to change the size and shape of the opening, the illumination field of the reticle R can be arbitrarily set.

In the reticle R of the present embodiment, reticle marks as alignment marks are formed at approximately the center of four sides of the pattern area PA surrounded by the light-shielding band. By projecting the images of these reticle marks on the resist layer of the wafer W, the images of the reticle marks are formed as latent images on the resist layer. In this embodiment, the reticle marks are
It is also used as an alignment mark when aligning each shot area of the wafer W with the reticle R. These four reticle marks have the same configuration (but in different directions). For example, one wafer mark is formed by forming a diffraction grating mark composed of seven dot marks arranged in the Y direction at a predetermined interval in the X direction. Are multi-marks arranged in five rows. These wafer marks are formed by a light shielding portion such as chrome in a transparent window provided in a light shielding band of the reticle R. Further, on the reticle R, an alignment mark composed of two cross-shaped light-shielding marks is formed near the outer periphery thereof so as to face each other. These two alignment marks are used for alignment of the reticle R (alignment of the projection optical system 13 with respect to the optical axis AX).

The reticle R is mounted on a reticle stage RS which can be finely moved by the motor 12 in the direction of the optical axis AX of the projection optical system 13 and which can be two-dimensionally moved and minutely rotated in a horizontal plane perpendicular to the optical axis AX. Is placed. A moving mirror 11m for reflecting a laser beam from a laser light interferometer (laser interferometer) 11 is provided at an end of the reticle stage RS.
Is fixed, and the two-dimensional position of the reticle stage RS is always detected by the laser interferometer 11 with a resolution of, for example, about 0.01 μm. Reticle alignment systems (RA systems) 10A and 10B are arranged above reticle R, and these RA systems 10A and 10B
Is to detect two cross-shaped alignment marks formed near the outer periphery of. By finely moving reticle stage RS based on the measurement signals from RA systems 10A and 10B, reticle R is positioned such that the center point of pattern area PA coincides with optical axis AX of projection optical system 13.

The illumination light IL that has passed through the pattern area PA of the reticle R enters the projection optical system 13 that is telecentric on both sides, and is projected onto the reticle R circuit pattern that has been reduced to 1/5 by the projection optical system 13. However, a resist layer is formed on the surface, and the surface is superimposed and projected (imaged) on one shot area on the wafer W held so that the surface substantially coincides with the best imaging plane of the projection optical system 13. .

The wafer W is vacuum-sucked on a micro-rotatable wafer holder (not shown), and is held on the wafer stage WS via the wafer holder. The wafer stage WS is configured to be two-dimensionally movable by a motor 16 in a step-and-repeat manner.
When transfer exposure of reticle R to one shot area is completed, wafer stage WS is stepped to the next shot position. A movable mirror 15 for reflecting a laser beam from the laser interferometer 15 is provided at an end of the wafer stage WS.
m is fixed, and the two-dimensional coordinates of the wafer stage WS are constantly detected by the laser interferometer 15 with a resolution of, for example, about 0.01 μm. The laser interferometer 15
It measures one direction perpendicular to the optical axis AX of the projection optical system 13 of the wafer stage WS (this is defined as an X direction) and coordinates in the Y direction perpendicular to the direction. The coordinates in the X direction and the Y direction are used. A stage coordinate system (stationary coordinate system) (X, Y) of wafer stage WS is determined. That is, the coordinate value of the wafer stage WS measured by the laser interferometer 15 is a coordinate value on the stage coordinate system (X, Y).

On the wafer stage WS, a reference member (glass substrate) 14 having a reference mark used for measuring a baseline amount (to be described later) or the like is approximately the same height as the exposure surface of the wafer W. It is provided as follows. The reference member 14 includes, as reference marks, a slit pattern composed of five sets of light-transmissive L-shaped patterns and two sets of reference patterns formed of light-reflective chrome (duty ratio is 1:
1) is provided. One set of reference patterns is
A diffraction grating mark in which seven dot marks arranged in the Y direction are arranged in three rows in the X direction, a diffraction grating mark in which three linear patterns are arranged in the X direction, and a diffraction grating mark 12 extending in the Y direction. The bar marks of the book are arranged in the X direction. The other set of reference patterns is obtained by rotating the one set of reference patterns by 90 °.

The slit pattern formed on the reference member 14 is illuminated from below (inside the wafer stage) by the illumination light (exposure light) transmitted below the reference member 14 using an optical fiber (not shown) or the like. It is configured to: The illumination light transmitted through the slit pattern of the reference member 14 forms a projected image of the slit pattern on the back surface (pattern surface) of the reticle R via the projection optical system 13. Further, the illumination light passing through any of the four reticle marks on the reticle R reaches the beam splitter 4 through the main condenser lens 9, the relay lenses 7, 5, and the like.
Illumination light transmitted through the beam splitter 4 is received by a photoelectric detector 35 disposed near a pupil conjugate plane of the projection optical system 13. The photoelectric detector 35 outputs a photoelectric signal SS corresponding to the intensity of the illumination light to the main control system 18. Hereinafter, an optical fiber (not shown), the reference member 14 and the photoelectric detector 3
5 are collectively called an ISS (Imaging Slit Sensor) system.

In FIG. 2, there is also provided an image forming characteristic correcting section 19 which can adjust the image forming characteristics of the projection optical system 13.
In the present embodiment, the imaging characteristic correction unit 19
Part 3 of the lens element, in particular, reticle R
By independently driving (moving or tilting in a direction parallel to the optical axis AX) each of a plurality of lens elements close to the optical element AX using a piezoelectric element such as a piezo element, For example, it corrects the projection magnification and distortion.

Next, an off-axis type alignment sensor (hereinafter referred to as "Field Imag") is provided beside the projection optical system 13.
e Alignment system (FIA system) ”). In this FIA system, light generated by the halogen lamp 20 is passed through a condenser lens 21 and an optical fiber 22.
The light is guided to the interference filter 23 through the filter and cuts out the light in the photosensitive wavelength range and the infrared wavelength range of the resist layer. The light transmitted through the interference filter 23 is incident on a telecentric objective lens 27 via a lens system 24, a beam splitter 25, a mirror 26, and a field stop BR. Light emitted from the objective lens 27 is reflected by a prism (or mirror) 28 fixed around the lower part of the lens barrel of the projection optical system 13 so as not to block the illumination visual field of the projection optical system 13, and makes the wafer W substantially vertical. Irradiation.

The light from the objective lens 27 is applied to a partial area including the wafer mark (base mark) on the wafer W, and the light reflected from the area is reflected by the prism 28, the objective lens 27, the field stop BR, and the mirror 26. , Beam splitter 25 and lens system 29 to guide plate 30. Here, the index plate 30 is disposed in a plane conjugate with the wafer W with respect to the objective lens 27 and the lens system 29, and an image of a wafer mark on the wafer W is formed in a transparent window of the index plate 30. Further, the index plate 30 is formed such that two linear marks extending in the Y direction are arranged at predetermined intervals in the X direction as index marks in the transparent window.
The light that has passed through the index plate 30 is transmitted to the first relay lens system 31,
The light is guided to an image sensor (CCD camera or the like) 34 via the mirror 32 and the second relay lens system 33, and the image of the wafer mark and the image of the index mark are formed on the light receiving surface of the image sensor 34. The imaging signal SV from the imaging element 34 is transmitted to the main control system 1
The position (coordinate value) of the wafer mark in the X direction is calculated here. Although not shown in FIG. 2, in addition to the FIA system (X-axis FIA system) having the above configuration,
Another set of FIA for detecting mark position in Y direction
A system (FIA system for the Y axis) is also provided.

Next, TT is located on the upper side of the projection optical system 13.
An L (through-the-lens) type alignment sensor 17 is also disposed, and the light for position detection from the alignment sensor 17 is projected onto the projection optical system 1 via mirrors M1 and M2.
It is led to 3. The light for position detection is the projection optical system 1.
3 is reflected on a wafer mark on the wafer W via the projection mark 3 and reflected light from the wafer mark is reflected on the alignment sensor 17 via the projection optical system 13, the mirror M2 and the mirror M1.
Is returned to. The alignment sensor 17 obtains the position of the wafer mark on the wafer W from the signal obtained by photoelectrically converting the returned reflected light.

FIG. 3 shows a detailed configuration of the TTL type alignment sensor 17 in FIG. 2. In FIG. 3, the alignment sensor 17 of this embodiment is a two-beam interference type alignment system (hereinafter referred to as "LIA system"). ) And a laser step alignment type alignment system (hereinafter, referred to as “LSA system”) in which the optical members are shared as much as possible. Although a brief description will be given here, a more specific configuration is disclosed in Japanese Patent Application Laid-Open No. 2-272305.

In FIG. 3, a laser beam emitted from a light source (such as a He—Ne laser light source) 40 is split by a beam splitter 41, and the reflected laser beam is transmitted through a shutter 42 to a first beam shaping optical system. (LI
A optical system) 45. On the other hand, the laser beam transmitted through the beam splitter 41 enters a second beam shaping optical system (LSA optical system) 46 via a shutter 43 and a mirror 44. Therefore, the shutters 42 and 43
Can be switched and used between the LIA system and the LSA system.

The LIA optical system 45 includes two sets of acousto-optic modulators and emits two laser beams having a predetermined frequency difference Δf approximately symmetrically with respect to the optical axis.
Further, the two laser beams emitted from the LIA optical system 45 reach a beam splitter 49 via a mirror 47 and a beam splitter 48, and the two laser beams transmitted therethrough are converted into a lens system (an inverse Fourier transform lens). 5
The light is incident on the reference diffraction grating 55 fixed on the apparatus from two different directions at a predetermined crossing angle via the mirror 3 and the mirror 54 to form an image (crossover). The photoelectric detector 56 receives the interference light of the diffracted lights transmitted through the reference diffraction grating 55 and generated in substantially the same direction, and outputs a sinusoidal photoelectric signal SR corresponding to the intensity of the diffracted light to the main control system 18 (FIG. LI)
Output to the A operation unit 58.

On the other hand, the two laser beams reflected by the beam splitter 49 intersect once at the opening of the field stop 51 by the objective lens 50, and then intersect with the mirror M2 (FIG. 2).
The mirror M1 in the middle enters the projection optical system 13 via an unillustrated illustration). Further, the two laser beams incident on the projection optical system 13 are substantially symmetrical with respect to the optical axis AX on the pupil plane of the projection optical system 13 and are once focused into a spot shape. Parallel light beams are inclined at symmetrical angles with respect to the direction (Y direction) with respect to the optical axis AX, and are incident on the wafer mark from two different directions at a predetermined intersection angle. One-dimensional interference fringes moving at a speed corresponding to the frequency difference Δf are formed on the wafer mark, and ± 1st-order diffracted light (interference light) generated in the same direction from the mark, here, in the optical axis direction is projected onto the wafer. The light is received by the photoelectric detector 52 via the system 13, the objective lens 50, and the like, and the photoelectric detector 52 outputs a sinusoidal photoelectric signal S corresponding to the cycle of the light-dark change of the interference fringe.
Dw is output to the LIA operation unit 58. The LIA operation unit 58 calculates the position shift amount of the wafer mark from the phase difference on the waveforms of the two photoelectric signals SR and SDw, and calculates the position shift amount using the position signal PDs from the laser interferometer 15. The coordinate position of wafer stage WS at which it becomes zero is obtained, and this information is output to alignment data storage unit 61 (see FIG. 4).

The LSA optical system 46 includes a beam expander, a cylindrical lens, and the like. The laser beam emitted from the LSA optical system 46 enters the objective lens 50 via beam splitters 48 and 49. Further, the laser beam emitted from the objective lens 50 once converges in a slit shape at the opening of the field stop 51, and then enters the projection optical system 13 via the mirror M2. The laser beam that has entered the projection optical system 13 passes through substantially the center of the pupil plane, and then extends in the X direction within the image field of the projection optical system 13, and forms an elongated strip-shaped spot light directed toward the optical axis AX. Projected onto W.

When the spot light and the wafer mark (diffraction grating mark) on the wafer W are relatively moved in the Y direction, light generated from the wafer mark is transmitted to the photoelectric detector via the projection optical system 13, the objective lens 50 and the like. Light is received at 52. The photoelectric detector 52 detects ± 1 order to ± 1 order of the light from the wafer mark.
Only the third-order diffracted light is photoelectrically converted, and a photoelectric signal SDi corresponding to the light intensity obtained by the photoelectric conversion in this manner is transmitted to the main control system 18.
Is output to the LSA calculation unit 57 in the above. The LSA calculation unit 57 has a position signal PDs from the laser interferometer 15.
The LSA calculation unit 57 samples the photoelectric signal SDi in synchronization with an up / down pulse generated for each unit movement amount of the wafer stage WS. Furthermore, LS
The A operation unit 57 converts each sampled value into a digital value and stores it in a memory in the order of addresses, then calculates the position of the wafer mark in the Y direction by a predetermined operation, and stores this information in the alignment data storage of FIG. Output to the unit 61.

Next, the configuration of the main control system 18 shown in FIG. 2 will be described with reference to FIG. FIG. 4 shows the main control system 18 of the present embodiment and the members related thereto. In FIG.
Arithmetic unit 57, LIA arithmetic unit 58, FIA arithmetic unit 59, waveform data storage circuit 60, alignment data storage unit 61, EGA operation unit 62, storage unit 63, shot map data unit 64, system controller 65, wafer stage controller 66, The reticle stage controller 67 constitutes the main control system 18. Among these members, the waveform data storage circuit 6
0 indicates the LSA operation unit 57 and the LIA operation unit 5
8 and the photoelectric signal S supplied to the FIA operation unit 59
This is a circuit for storing the waveforms of Di, SR and SV as digital data. Then, the LSA operation unit 57, L
The IA operation unit 58 and the FIA operation unit 59
If necessary, the corresponding photoelectric signal is read from the waveform data storage circuit 60, the coordinate position of each wafer mark in the stage coordinate system (X, Y) is obtained, and the obtained coordinate position is stored in the alignment data storage unit 61. Supply. The information of the measured coordinate position in the alignment data storage unit 61 is E
It is supplied to the GA operation unit 62.

The shot map data storage unit 64 stores design coordinate values of the wafer marks belonging to each shot area on the wafer W in the coordinate system (x, y) on the wafer W. Are also supplied to the EGA operation unit 62. The EGA operation unit 62 calculates the stage coordinate system (X) from the designed array coordinate values in the coordinate system (x, y) on the wafer W by the least square method based on the measured coordinate values and the designed coordinate values. , Y) to obtain six conversion parameters (corresponding to the conversion parameters a to f of (Equation 1)) for obtaining the calculated array coordinate values,
The conversion parameters a to f and the residual error component when these conversion parameters are used (in this example, a simple sum of squares of the residual between the design value and the measured value) are supplied to the storage unit 63.

At this time, the system controller 65
Signal processing conditions (described later) for the LSA operation unit 57, LIA operation unit 58, and FIA operation unit 59
Is changed variously, and the coordinate position of the wafer mark is repeatedly calculated. In response to this, the EGA calculation unit 62 obtains the conversion parameters a to f and the residual error component, respectively. Then, the EGA calculation unit 62 causes the storage unit 63 to store the conversion parameters a to f when the residual error component is finally minimized and the signal processing conditions at this time. Further EG
The A operation unit 62 uses the conversion parameters a to f stored as described above to convert a design array coordinate value in the coordinate system (x, y) on the wafer W into a stage coordinate system (X, Y). The calculated array coordinate values are obtained, and the calculated array coordinate values are supplied to the system controller 65.

In response, the system controller 65
2 drives the wafer stage WS of FIG. 2 via the motor 16 while monitoring the measurement values of the laser interferometer 15 via the wafer stage controller 66 to determine the position of each shot area on the wafer W and each shot area. Exposure to Further, the system controller 65 communicates with the laser interferometer 11 via the reticle stage controller 67.
While monitoring the measured values of FIG.
Is driven to adjust the position of the reticle R.

Next, the operation of positioning the respective shot areas on the wafer W and projecting and exposing the pattern image of the reticle R to the respective shot areas in this embodiment will be described. First, the arrangement of shot areas on the wafer W, the shape of a wafer mark as an alignment mark, and the like will be described. FIG.
5A shows an arrangement of shot areas on the wafer W. In FIG. 5A, the shot areas are regularly arranged on the wafer W along a coordinate system (x, y) set on the wafer W. ES1, ES2,..., ESN are formed, and a chip pattern is formed in each shot region ESi by the steps up to that. In addition, each shot area ESi
Are separated by a street line having a predetermined width in the x direction and the y direction, and a wafer mark Mxi in the X direction as an alignment mark is formed at the center of the street line extending in the x direction near each shot area ESi. A wafer mark Myi in the Y direction is formed at the center of a street line extending in the y direction near each shot area ESi. The wafer marks Mxi and Myi are each x
Three linear patterns are arranged at predetermined pitches in the direction and the y direction. These patterns are formed as patterns of concave portions or convex portions on the lower portion of the wafer W.

When exposing the wafer W, nine shot areas indicated by oblique lines are selected from the shot areas ESi. Assuming that the shot areas selected in this way are sample shots SA1 to SA9, wafer marks Mxi and Myi are formed close to each sample shot SAi, respectively. In this example, the coordinate positions of the sample shots SA1 to SA9 on the stage coordinate system (X, Y) are measured by measuring the positions of the wafer marks Mxi and Myi. Specifically, an imaging signal of the wafer mark Mx1 is supplied to, for example, the FIA operation unit 59 of FIG. 4 via the imaging device 34 of FIG. 2, and the FIA operation unit 59 outputs the wafer mark MX1 based on the set measurement parameters. Is detected in the X direction.

FIG. 5B shows another example of a wafer mark. In FIG. 5B, a wafer mark MAX having a diffraction grating pattern having a predetermined pitch in the X direction which is the measurement direction is formed. Have been. This wafer mark M
In order to detect the position of Ax, the two laser beams BM ₁ and BM ₂ emitted from the LIA optical system 45 (see FIG. 3) in the alignment sensor 17 of FIG. Irradiate on top. Its pitch in the X direction of the crossing angle and the wafer mark MAx is the laser beam BM ₁ -1 order diffracted light B ₁ from the wafer mark MAx by (-1) and the laser beam BM ₂ +1 order diffracted light B ₂ from the wafer mark MAx by (+) Is set to be parallel. The interference light of the −1st-order diffracted light B ₁ (-1) and the + _1st-order diffracted light B ₂ (+) is converted into a photoelectric signal SDw by the photoelectric detector 52 in FIG. 3, and this photoelectric signal SDw is supplied to the LIA operation unit 58. In the LIA operation unit 58,
From the phase difference between the photoelectric signal SR as the reference signal and the photoelectric signal SDw, the amount of displacement of the wafer mark Max in the X direction is calculated.

FIG. 5 (c) shows still another example of the wafer mark. In FIG. 5 (c), a dot mark arranged at a predetermined pitch in the Y direction perpendicular to the X direction which is the measurement direction is shown. Is formed.
In order to detect the position of the wafer mark MBy, the LSA optical system 46 (see FIG. 3) in the alignment sensor 17 shown in FIG.
The laser beam emitted from the laser beam is irradiated as a slit-shaped spot light LYS long in the Y direction near the wafer mark MBy. Then, when the wafer mark WSy is scanned with respect to the spot light LYS by driving the wafer stage WS shown in FIG. 2, in a range where the spot light LYS scans over the wafer mark MBy, a predetermined direction from the wafer mark MBy. Diffracted light is emitted. A photoelectric signal SDi obtained by photoelectrically converting the diffracted light by the photoelectric detector 52 in FIG.
The A operation unit 57 obtains the position of the wafer mark MBy in the X direction based on the set measurement parameters.

Next, the FIA operation unit 59 shown in FIG.
The signal processing conditions in the SA operation unit 57 and the LIA operation unit 58 will be described in detail. The signal processing conditions in this example indicate a waveform analysis algorithm, a slice level, a processing gate width, and the like. The processing gate width is a region of a predetermined width determined around the position of a wafer mark in design.

First, the signal processing conditions of the FIA operation unit 59 will be briefly described with reference to FIG. FIG. 6 (a)
6 shows a state of the wafer mark Mx1 imaged by the FIA image sensor 34 in FIG. 2, and FIG. 6B shows a waveform of an image signal obtained at that time. This imaging signal is stored in the waveform data storage circuit 60 of FIG. As shown in FIG. 6A, a wafer mark Mx1 composed of three linear patterns is formed in the imaging visual field VSA of the imaging element 34, and is formed on the index plate 30 of FIG. Index mark F
M1 and FM2 are arranged. The imaging element electrically scans the images of the wafer mark Mx1 and the index marks FM1 and FM2 along the horizontal scanning line VL. At this time, since the single scanning line is disadvantageous in terms of the SN ratio, the level of the imaging signal obtained by a plurality of horizontal scanning lines falling within the imaging visual field VSA can be averaged for each pixel in the horizontal direction. desirable.

As shown in FIG. 6B, on both sides of the obtained image signal, there are concave portions corresponding to the index marks FM1 and FM2, respectively. The FIA operation unit 59 detects these concave portions at the slice level SL2. The center positions of the two concave portions on the pixel are obtained. Then, as the center of their two center positions, determining the reference position x ₀ of when based on the index marks FM1, FM2. Note that the index marks FM1,
Instead of finding each center position of FM2, an index mark FM
And a position of the left edge of the index marks FM2 one of the right edge may be calculated the reference position x _0.

As shown in FIG. 6 (b), the waveform of the portion corresponding to the wafer mark Mx1 in the image pickup signal has a concave portion at a position corresponding to the left edge and the right edge of each linear pattern. I have. The FIA operation unit 59 detects the concave portion corresponding to the wafer mark Mx1 of the imaging signal at the slice level SL1, finds the center position of each linear pattern, and averages each center position to obtain the wafer mark Mx.
Calculating a first measurement position x _c. Then, the difference Δ between the previously obtained reference position x ₀ and the measurement position x _c of the wafer mark Mx1 is calculated.
x (= x ₀ −x _c ) is calculated, and the imaging region V in FIG.
A value obtained by adding the difference Δx to the coordinate position of wafer stage WS when wafer mark Mx1 is positioned in SA is supplied to alignment data storage unit 61 in FIG. 4 as mark position information.

Therefore, in the FIA operation unit 59, the signal processing conditions that can be changed include a waveform analysis algorithm, a slice level SL1, a contrast limit value, and a processing gate width GX (width G on a pixel) shown in FIG.
x center position and its width). Further, as a waveform analysis algorithm, for example, as disclosed in Japanese Patent Application Laid-Open No. 4-65603, when calculating the center position of each linear pattern, as shown in FIG. Slope section B corresponding to edge and right edge
Mode using only the outer slope portions BS _1L and BS _{2R of} S _1L and BS _2L and BS _1R and BS _2R , inner slope portion B
Mode using only S _1R and BS _2L , outer slope section BS
There is a mode using _1L , BS _2R and inner slope sections BS _1R , BS _2L .

Next, signal processing conditions in the LSA operation unit 57 will be described with reference to FIG. FIG. 7 (a)
FIG. 7 shows a state in which a wafer mark MBx composed of dot patterns arranged in the X direction is scanned by a slit-shaped spot light LXS long in the X direction by a laser beam.
(B) shows the waveform of the photoelectric signal obtained by the scanning. As the waveform analysis algorithm in the LSA operation unit 57, for example, there are three algorithms described below.

In the first algorithm, after the photoelectric signal is smoothed as shown in FIG. 7B within the section of the predetermined processing gate width, the obtained signal waveform is sliced at the set slice level Vr. I do. Then, FIG.
As shown in (1), if there are intersections on the left and right of the signal waveform, the center point of these two intersections is detected as the mark position.

[0052] In the second algorithm, set after the photoelectric signal is so smoothed signal waveform at a predetermined level L ₁ or more sections, a plurality of slice levels between the level L ₂ close to the peak value at regular intervals Then, intersections at each slice level and their intervals are obtained. Then, based on the intervals at each slice level, a slice level at which the slope of the signal waveform is maximum in a portion below a preset level is selected, and the center point of the intersection at that level is detected as a mark position. is there.

In the third algorithm, the signal waveform is sliced at the set slice level, and the center position between two intersections is determined as a reference position. Then, after the photoelectric signal is so smoothed signal waveform at a predetermined level L ₁ or more sections, and setting a plurality of slice levels between the level L ₂ close to the peak value at regular intervals, at each slice level And the midpoint difference (that is, the difference between the center points at adjacent slice levels). And
A region where the center point at each slice level is not far from the previously obtained reference position and each center point is stable (that is, the midpoint difference is small and the slice level is the longest continuous) Area), and a center point in the area is detected as a mark position. As a result, even when the obtained photoelectric signal becomes asymmetric as shown in FIGS. 7C to 7E, the mark position can be accurately obtained.

Next, the signal processing conditions in the LIA operation unit 58 will be described with reference to FIG. In this example, the description will be made based on the heterodyne method. As shown in FIG. 8, two coherent laser beams (parallel light beams) BM ₁ and BM ₂ having a frequency difference Δf intersect with a diffraction grating wafer mark MAX having a one-dimensional pitch 2P on the wafer. When incident at 2 · φ _0, in the wafer mark MAx is one-dimensional interference fringes IF pitch P is generated. This interference fringe IF moves in the pitch direction of the wafer mark MAX in accordance with the frequency difference Δf, and its moving speed V becomes (V = Δf ·
P). As a result, the wafer mark M
Ax generates diffracted light beams B ₁ (-1), B ₂ (+1), and ‥‥. In this case, the suffixes 1 and 2 mean diffracted light from the incident laser beams BM ₁ and BM ₂ , respectively.
The numbers in parentheses indicate the diffraction orders.

Normally, in the LIA system, ± first-order diffracted lights B ₁ (−1) and B ₂ (+1) that travel along the optical axis AX of the projection optical system 13.
The position shift of the wafer mark MAX is detected by calculating the phase difference between the photoelectric signal of the interference light and the photoelectric signal of the reference interference light separately generated from the two light transmission beams. In addition, the zero-order diffracted light B ₂ (0) and the _second-order diffracted light B
₁ (-2), the amount of displacement detected from the phase difference between the photoelectric signal of the interference light and the reference photoelectric signal, and the 0th-order diffracted light B ₁ (0) and −
The position shift amount detected from the phase difference between the photoelectric signal of the interference light with the _second-order diffracted light B ₂ (+2) and the reference photoelectric signal may be averaged to obtain the position shift amount.

Therefore, the only signal processing condition that can be changed by the LIA operation unit 58 is the interference light (the order of the diffracted light) to be photoelectrically detected. That is, in the LIA system, ± 1st-order diffracted light B
_1st mode using ₁ (-1) and B ₂ (+1), 0th-order diffracted light B
The second mode using ₂ (0), the _second-order diffracted light B ₁ (-2), and the zero-order diffracted light B ₁ (0) and the _second-order diffracted light B ₂ (+2), furthermore, the first mode and the second mode A third method is to compare the intensities of the interference lights in each of the two modes and select and use the one with the greater intensity value.
There is a mode. When optimizing the LIA system, these three
The two modes are switched to detect the position of the wafer mark.

Next, with reference to the flowchart of FIG. 1, an example of the overall operation when exposing the pattern image of the reticle R to each shot area ESi of the wafer W of FIG. Will be described. In this example, a so-called enhanced global alignment (hereinafter referred to as “EG
A)). First, in step 101 of FIG. 1, the measurement signal waveforms of the wafer marks (alignment marks) Mxi and Myi belonging to the nine sample shots SA1 to SA9 of FIG. 5A are taken into the waveform data storage circuit 60 of FIG. As the measurement sensor in this case, for example, an FIA system including the image sensor 34 in FIG. 2 is used, but depending on the shape of the wafer mark, an LIA system or an LSA system is also used. Thereafter, in step 102, the system controller 6 shown in FIG.
5 is a signal processing condition for the FIA operation unit 59;
That is, the values of the measurement parameters such as the waveform analysis algorithm and the slice level are set to the initial state.

In response, in step 103,
The FIA operation unit 59 processes the measurement signal read from the waveform data storage circuit 60, and processes each of the wafer marks Mx
The coordinate values of i and Myi in the stage coordinate system (X, Y) are calculated. The measured coordinate values are supplied to the EGA calculation unit 62 via the alignment data storage unit 61 in FIG.
2 are six conversion parameters a satisfying (Equation 1) from the design coordinate values of the wafer mark and the measured coordinate values.
Ｆf are obtained using a simple least squares method. This is E
This is a calculation called GA calculation.

Next, in step 105, the EGA calculation unit 62 calculates a residual error component between the calculated array coordinate value calculated using the conversion parameters a to f obtained in step 104 and the measured coordinate value, that is, The sum of squares of the residual between the calculated array coordinate value and the measured coordinate value is obtained. Assuming that the calculated coordinate value of the wafer mark Mxn in the X direction is X _n , and the measured coordinate value is XM _n , Y of the wafer mark Myn
The calculated coordinate value of the direction is Y _n , and the measured coordinate value is YM
_{If n} , the residual error component in the EGA method is defined as follows. However, the value of m is 9.

[0060]

(Equation 2)

Since this is the first EGA calculation, EG
After storing the obtained conversion parameters a to f and the residual error component in the storage unit 63, the A operation unit 62 proceeds to step 106 and sets the value P of the set measurement parameter.
₁ is also stored in the storage unit 63. Then, step 10
In step 7, the EGA calculation unit 62 checks whether to change the measurement parameter. If the measurement parameter is to be changed, the value of the measurement parameter is changed by a predetermined value in step 108, and the process returns to step 103.

Then, the FIA operation unit 59 uses the updated measurement parameters to generate the waveform data storage circuit 60.
Processing the measurement signal read from the
The coordinate values of xi and Myi in the stage coordinate system (X, Y) are calculated. Then, in step 104, the EGA arithmetic unit 62 calculates the values of the six conversion parameters a to f satisfying (Equation 1) from the design coordinate values and the measured coordinate values of the wafer mark by the least square method. Determine using

Next, in step 105, the EGA calculation unit 62 calculates a residual error component between the calculated array coordinate value calculated using the conversion parameters a to f obtained in step 104 and the measured coordinate value. , Is compared with the residual error component stored in the storage unit 63. Then, if the current residual error component is equal to or larger than the stored residual error component, the operation proceeds to step 107. On the other hand, when the current residual error component is smaller than the stored residual error component, that is, when the residual error component is the smallest among the residual error components obtained so far, the EGA calculation unit 62 determines the calculated conversion parameters a to f. And after storing the residual error component in the storage unit 63,
The process proceeds to step 106, where the storage unit 63 also stores the measurement parameter value P ₂ set this time.

Thereafter, when the measurement parameters are changed in Step 107, Steps 108 to
7 are repeated, and in step 107, when the measurement parameter is not changed any more, step 1
At 09, the system controller 65 checks whether there is any other measurement parameter to be evaluated. If there is another measurement parameter to be evaluated, the system controller 65 instructs the EGA calculation unit 62 at step 110 to indicate the type of the measurement parameter to be changed for the evaluation. In response to this, the EGA calculation unit 62 changes the type of the measurement parameter to be evaluated, and
The operation 08 is repeated, and the conversion parameters a to f when the residual error component is minimized, the minimum residual error component and the value of the measurement parameter at that time are stored in the storage unit 62.

In step 109, when there are no more measurement parameters to be evaluated, the operation proceeds to step 111, and the EGA operation unit 62 determines the conversion parameters a to f and each shot when the residual error is minimized. The calculated array coordinate value of each shot area ESi is obtained by substituting the designed array coordinate value of the area ESi into (Equation 1). In addition, a baseline amount, which is an interval between the measurement center of the alignment sensor of the FIA system, the LIA system, and the LSA system, and the reference point in the exposure field of the projection optical system 13 is obtained in advance. Therefore, in step 112, the system controller 65 sequentially positions each shot area ESi based on the calculated coordinate values obtained by correcting the array coordinates calculated by the EGA operation unit 62 with the baseline amount. Then, the pattern image of the reticle R is exposed.

After the exposure of all shot areas of one wafer W is completed, the wafer W is unloaded. After that, the measurement parameters are automatically optimized in accordance with the flow of FIG. 1 for the wafers waiting in the same lot, and then the wafers are exposed. However,
Since the tendency of measurement signals obtained in the same lot is often similar, the measurement parameters determined for the first wafer should be used for the second and subsequent wafers in the same lot. You may.

In the above-described embodiment, the condition for minimizing the residual error component is used for optimizing the measurement parameters. In addition, for example, the scaling parameters a and f among the conversion parameters a to f are used. A method of optimizing the measurement parameters so that d is closest to the measured value is also conceivable. That is, as can be seen from (Equation 1), the scaling parameters a and d are parameters representing the amount of linear expansion and contraction of the wafer. In this case, two marks are formed at predetermined intervals on the wafer in advance, and the distance between these two marks is measured before the second and subsequent exposures. Can be estimated. Therefore, in step 105 of FIG. 1, instead of checking whether the residual error component is the minimum, the deviation between the scaling parameters a and d among the conversion parameters a to f obtained in step 104 and the estimated value is calculated. May be obtained, and the measurement parameters may be optimized such that the sum of the squares is minimized.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the projection exposure apparatus shown in FIGS. 2 to 4 is used. In this embodiment, the EG used in the first embodiment is used.
A first weighted enhanced global alignment method (hereinafter, referred to as “W1-EGA method”), which is a further improved alignment of the A method, is performed. In the W1-EGA type alignment, weighting is performed according to the distance from the sample shot as described later.

FIG. 9 shows a wafer W to be exposed in this example. In FIG. 9, when determining the calculated coordinate position of the i-th shot area ESi on the wafer W, the shot areas ESi and m number in accordance with the distance LK1~LK9 between the sample shots SA1~SA9 of (m = 9 in FIG. 9), the weight W _in each of the measured coordinate positions of the nine sample shots (alignment data) Given. Therefore, in this W1-EGA system, EG
Instead of the residual error component of (Formula 2) in the A system, a residual error component Ei of the following (Formula 3) is defined.

[0070]

(Equation 3)

Then, the conversion parameter a of (Equation 1) is set such that the residual error component Ei defined in this manner is minimized.
Are determined. Here, the sample shots SA1 to SA9 used for each shot area ESi are the same, but the distance to each sample shot SAn is naturally different for each shot area ESi. Therefore, the coordinate position (alignment data) of the sample shot SAn
The weight W _in is changed for each shot area ESi give in.
Then, conversion parameters a to f are set for each shot area ESi.
Is determined, and the calculated coordinate position is calculated from (Equation 1), whereby the calculated array coordinates (shot array) of all shot areas on the wafer W are determined.

As described above, in the W1-EGA system, the wafer W
For each shot area ESi above, each sample shot S
The weight W _in changes to the An of the coordinate data. The weight W _in an example, i-th shot area ESi and n
It is expressed as follows as a function of the distance LKn from the sample shot SAn. However, the parameter S is a parameter for changing the degree of weighting.

[0073]

(Equation 4)

[0074] As is clear from this (number 4), as the i-th distance LKn short sample shot SAn to the shot area ESi, so that the weight W _in giving to the alignment data becomes large. Also, in (Equation 4), when the value of the parameter S is sufficiently large, the result of the statistical operation processing is substantially equal to the result obtained by the EGA method of the first embodiment. On the other hand, if all shot areas ESi to be exposed on the wafer are sample shots SAn and the value of the parameter S is sufficiently close to zero, a so-called die-by-die measurement is performed for measuring the position of the wafer mark for each shot area. -It is almost equal to the result obtained by the die method.
That is, in the W1-EGA system, by setting the parameter S to an appropriate value, an intermediate effect between the EGA system and the die-by-die system can be obtained. For example, for a wafer having a large non-linear component, by setting the value of the parameter S small, it is possible to obtain an effect (alignment accuracy) substantially equal to the die-by-die method, and to reduce an alignment error due to the non-linear component. It can be removed well. Further, when the measurement reproducibility of the alignment sensor is poor, by setting a large value of the parameter S, it is possible to obtain substantially the same effect as in the EGA method, and it is possible to reduce the alignment error by the averaging effect. .

Further, the weighting function of (Equation 4) is defined by the wafer mark Mxi for the X direction and the wafer mark My for the Y direction.
i and are separately prepared, so that the weight Win can be set independently _in the X direction and the Y direction. Therefore, the degree (large or small) of the nonlinear distortion of the wafer,
Even if the regularity or the step pitch, that is, the distance between the centers of two adjacent shot areas (although depending on the width of the street line on the wafer, a value substantially corresponding to the shot size) is different between the X direction and the Y direction. By independently setting the value of the parameter S, the shot arrangement error on the wafer can be corrected with high accuracy. At this time, the value of the parameter S may be different between the X direction and the Y direction as described above, and even if the value of the parameter S in the X direction and the Y direction is the same or different, The value of S may be appropriately changed according to the magnitude of the “regular nonlinear distortion”, regularity, step pitch, measurement reproducibility of the alignment sensor, and the like.

As described above, the effect can be changed from the EGA system to the die-by-die system by appropriately changing the value of the parameter S. Therefore, alignment is performed for various layers and further for each component (X direction and Y direction) in accordance with, for example, characteristics of nonlinear components (for example, magnitude, regularity, etc.), step pitch, and the reproducibility of measurement of the alignment sensor. The alignment can be flexibly changed, and alignment can be performed under optimum conditions for each layer and each component.

An example of the operation when the present invention is applied to the above-described W1-EGA method will be described. That is, in this case, corresponding to step 104 in FIG. 1, the residual error component Ei defined by (Equation 3) is minimized (extreme).
The values of the conversion parameters a to f in (Equation 1) are determined. Then, corresponding to step 105, the conversion parameters a to f when the residual error component Ei obtained so far is minimized.
Is adopted. Other operations are the same as in the first embodiment. Accordingly, in this example, signal processing conditions such as measurement parameters and the value of the parameter S are optimized so that the weighted residual error component Ei of (Equation 3) is minimized.

Next, with reference to FIG. 10, a description will be given of the alignment method of the second weighted Enhanced Global Alignment method (hereinafter referred to as "W2-EGA method"). Here, for the sake of simplicity, it is assumed that non-linear distortion, particularly point-symmetric, occurs regularly in the wafer W, and the center of the point symmetry coincides with the center of the wafer W (wafer center).

FIG. 10 shows a wafer W to be exposed in this example. In FIG. 10, a deformation center point of the wafer W (a point symmetric center of nonlinear distortion), that is, a wafer center Wc,
Let LEi be the distance (radius) between the i-th shot area ESi on the wafer W and the wafer center Wc and m (m = 9 in FIG. 10) sample shots SA1 to SA.
The distance (radius) between each of the light emitting elements 9 is LW1 to LW9. In this W2-EGA system, W1-EG
Like the A-system, in accordance with the distance LEi and distance LW1～LW9, giving a weight W _in 'to each of the alignment data of the nine sample shots SA1～SA9. This W2
In the EGA method, after detecting two sets of wafer marks (Mxi, Myi) for each sample shot, (Equation 3)
Similarly, the residual error component Ei 'is defined by the following (Equation 5), and the values of the conversion parameters a to f of (Equation 1) are determined so that (Equation 5) is minimized.

[0080]

(Equation 5)

[0081] Similar to the W1-EGA method in this W2-EGA method, since the weight W _in providing the alignment data 'is to be changed for each shot area ESi, shot area E
The conversion parameters a to f are determined by performing a statistical operation for each Si, and the calculated array coordinate values are determined.
Then, for each shot area ESi on the wafer W, for changing the weight W _in 'for each sample shot,
The weight W _in 'in equation (5), expressed as a function distance (radius) LEi of the i-th shot area ESi and the wafer center Wc of the wafer W as follows. However, the parameter S is a parameter for changing the degree of weighting.

[0082]

(Equation 6)

As is apparent from (Equation 6), the distance L from the sample shot SAn to the wafer center Wc is
Wn is, the smaller the sample shot close to the distance LEi between the i-th shot area ESi on the wafer center Wc and the wafer W, the weight W _in 'to be given to the alignment data
Is becoming larger. In other words, the largest weight W _in 'is given to the sample shots alignment data located on a circle of radius LEi around the wafer enter Wc, the weight W for alignment data with distance radially from the circle _in ′ is smaller.

The value of the parameter S in (Equation 6) is the same as the W1-EGA method, which is required for the alignment accuracy, the characteristics of nonlinear distortion (for example, large and small, regularity, etc.), the step pitch, and the measurement reproduction of the alignment sensor. What is necessary is just to determine suitably according to the quality of sex. That is, when the nonlinear component is relatively large, by setting the value of the parameter S to be smaller, it is possible to reduce the influence of a sample shot having a significantly different distance LWn from the wafer center Wc. On the other hand, when the nonlinear component is relatively small,
By setting the value of the parameter S to be larger, it is possible to prevent a decrease in alignment accuracy in an alignment sensor (or a layer) having poor measurement reproducibility.

Further, in the W2-EGA system, a plurality of shot areas which are substantially equidistant from the point symmetry center on the wafer W, ie, a plurality of shot areas located on the same circle centered on the point symmetry center. in each, the weight W _in 'is the same given to the course of the sample shot alignment data. For this reason, when a plurality of shot areas are located on the same circle centered on the point symmetry center, the above-mentioned weighting and statistical calculation are performed on only one of the shot areas to convert the conversion parameters a to f. Once calculated, the coordinate positions of the remaining shot areas can be determined using the previously calculated parameters a to f as they are. This has the advantage that the amount of calculation for determining the coordinate position is reduced.

Incidentally, it is desirable that the arrangement of sample shots suitable for the W2-EGA method be specified so as to be symmetrical with respect to the point symmetric center of the nonlinear distortion, that is, the wafer center Wc. What is necessary is just to specify a character shape, a cross shape, etc. Besides that,
The arrangement may be the same as in the W1-EGA system. When the point of symmetry of the nonlinear distortion is other than the wafer center Wc, an X-shaped or cross-shaped arrangement based on the point of symmetry may be used. When determining the values of the conversion parameters a to f, the weighting function shown in (Equation 5) is expressed by X
It may be set independently in each of the direction and the Y direction.

When the present invention is applied when the alignment is performed by the W2-EGA method, the residual error component Ei 'of (Equation 5) is minimized (extreme value), for example, corresponding to step 104 in FIG. The conversion parameter a of (Equation 1)
What is necessary is just to obtain the value of -f. Then, corresponding to step 105, the values of the conversion parameters a to f and the value of the parameter S when the residual error component Ei 'is minimized may be adopted.

Next, the W1-EGA system and the W2-EGA
A method for determining a parameter S representing the degree of weighting in the method will be described. First, as an example, the value of the parameter S can be determined by the following equation. In this formula, D is a weighting parameter, by the operator to set the value of the weighting parameter D to a predetermined value, automatically parameter S, and thus the weight W _in, W _in 'is determined.

[0089]

S = D ² / (8 · log _e 10) The physical meaning of the weight parameter D is the range of sample shots effective for calculating the coordinate position of each shot area on the wafer (hereinafter simply referred to as “the range of sample shots”). "Zone").
That is, when the zone is large, the number of effective sample shots increases, and the result is close to the result obtained by the conventional EGA method. Conversely, when the zone is small, the number of valid sample shots is small, and the result is close to the result obtained by the die-by-die method. However, the zone referred to here is only a guide value for weighting, and even if all sample shots exist outside the zone, the sample shot closest to the shot area whose coordinate position should be determined The statistical calculation is performed by maximizing the weight of the alignment data.

The equation for determining the parameter S is not limited to (Equation 7). For example, the following (Equation 8) can be used. However, the area of the wafer is A [mm ² ], the number of sample shots is m, and the correction coefficient (positive real number) is C.

[0091]

S = A / (m · C) This (Equation 8) is obtained by reflecting a change in the wafer size (area) or the number of sample shots in the determination of the parameter S, and using a correction coefficient to be used in the determination. The optimum value of C does not change much. When the correction coefficient C is small, the value of the parameter S is large, which is close to the result obtained by the conventional EGA method. When the correction coefficient C is large, the value of the parameter S is small, so that the die-by-die Approach the results obtained with the method. Therefore, by simply inputting the correction coefficient C determined in advance by experiment or simulation into the exposure apparatus via the operator or the identification code reading device, the degree of weighting of the alignment data from (Equation 8), that is, (Equation 4) , the weight W _in which is determined by the (number 6), and W _in 'is automatically determined.

For this reason, various layers and furthermore each component (X
Direction and Y direction), the alignment is flexibly changed according to, for example, the characteristics of the non-linear component (for example, size, regularity, etc.), the step pitch, the reproducibility of the measurement of the alignment sensor, and the like. Alignment can be performed under optimal conditions. In particular, when (Equation 8) is used, even if the wafer size, the step pitch (shot size), the number of sample shots, and the like change, the coordinate positions of all shot areas on the wafer can be accurately determined regardless of the change. Positioning can always be performed with stable accuracy.

The present invention is not limited to the above-described embodiment, but can take various configurations without departing from the gist of the present invention.

[0094]

According to the present invention , the value obtained for each signal processing condition is obtained.
Any one of a set of conversion parameters
Exchange parameters are selected based on predetermined conditions.
Using a set of conversion parameters obtained, a plurality of
Calculates array information on each stationary coordinate system of the work area
Automatically optimize signal processing conditions.
Can be. Further, when the signal processing conditions are optimized so that the residual error component is minimized, there is an advantage that the signal processing conditions can be optimized while minimizing the alignment error.
In addition, since signal processing conditions that have been determined for each process can be automatically optimized, human errors can be prevented and errors can be reduced.

Further, for example, by optimizing the signal processing conditions for the first wafer in one lot and using the signal processing conditions thereafter, there is an advantage that a decrease in throughput can be prevented.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a first embodiment of a positioning method according to the present invention.

FIG. 2 is a configuration diagram illustrating a projection exposure apparatus to which the alignment method according to the first embodiment is applied.

FIG. 3 is a TTL alignment sensor 1 shown in FIG. 2;
7 is a block diagram showing a detailed configuration of FIG.

FIG. 4 is a block diagram showing a detailed configuration of a main control system 18 and the like in FIG. 2;

5A is a plan view showing an arrangement of shot areas on a wafer to be exposed in the first embodiment, FIG. 5B is an explanatory diagram of a method for detecting a wafer mark for an LIA system, and FIG. FIG. 4 is an explanatory diagram of a method of detecting a system wafer mark.

6A is a diagram illustrating an observation region of an image sensor of an FIA-based alignment sensor, and FIG. 6B is a waveform diagram illustrating an image signal corresponding to FIG. 6A.

7A is an enlarged plan view showing a wafer mark for an LSA-based alignment sensor and a spotlight for detection, FIG. 7B is a waveform diagram showing a detection signal corresponding to FIG. 7A, and FIG. FIGS. 7A to 7E are waveform diagrams illustrating examples of asymmetric detection signals.

FIG. 8 is an explanatory view of the principle when detecting the position of a wafer mark by an LIA-based alignment sensor.

FIG. 9 is a plan view showing an arrangement of sample shots on a wafer when performing alignment by a W1-EGA method in a second embodiment of the present invention.

FIG. 10 is a plan view showing an arrangement of sample shots on a wafer when performing alignment by the W2-EGA method.

[Explanation of symbols]

 Reference Signs List 1 Mercury lamp 3 Illumination optical system 9 Main condenser lens R Reticle 13 Projection optical system W Wafer WS Wafer stage 15 Laser interferometer 17 TTL type alignment sensor 18 Main control system ESi shot area SA1 to SA9 Sample shot Mx1 Wafer mark in X direction My1 Wafer mark in Y direction

Claims (11)

(57) [Claims] 1. A method according to claim 1 , further comprising the steps of:
In order to sequentially align each of the plurality of processing regions regularly arranged with respect to a predetermined processing position in a stationary coordinate system that defines the movement position of the substrate, the plurality of processing regions Measuring position information of at least three pre-selected processing regions on the stationary coordinate system,
By statistically calculating the measured plurality of position information , array information in the stationary coordinate system of each of the plurality of processed regions on the substrate is calculated, and each of the calculated plurality of processed regions is calculated. A method of positioning each of the plurality of processing regions with respect to the processing position by controlling a movement position of the substrate according to the array information , wherein the stationary coordinates of the at least three preselected processing regions When measuring position information on a system, a measurement signal obtained from a measurement object in the processing area is used as a first signal.
The first position information is obtained by processing under the signal processing condition, and the predetermined distribution is determined based on the first position information.
To calculate array information on the stationary coordinate system from column information
Is determined, and the measurement signal is converted to a second conversion parameter different from the first signal processing condition.
The second position information is obtained by processing under the signal processing conditions of No. 2 and the predetermined distribution is determined based on the second position information.
To calculate array information on the stationary coordinate system from column information
Is determined, and any one of the plurality of determined conversion parameters is determined.
A set of conversion parameters is selected based on predetermined conditions, and using the selected set of conversion parameters, array information on the stationary coordinate system of each of the plurality of processing regions on the substrate is calculated. A positioning method, characterized in that: 2. The method according to claim 1, wherein the predetermined condition is, for each of the set of transformation parameters, measured under the position information on the stationary coordinate system calculated using the transformation parameters and the signal processing condition. The method according to claim 1, further comprising: selecting a set of conversion parameters when the residual error component is minimized, including a residual error component with position information. 3. The predetermined condition includes a deviation between the set of conversion parameters and an estimated value of the conversion parameter, and selects the set of conversion parameters when the sum of squares of the deviation is minimized. The method according to claim 1, wherein: 4. The apparatus according to claim 1 , wherein a signal processing condition used when calculating the position information used in calculating the selected set of conversion parameters is stored. The alignment method described. 5. The newly measured measurement signal after the selection of the set of transformation parameters is made, the alignment method according to claim 4, wherein the treatment with the stored signal processing conditions . 6. The method according to claim 1, wherein the signal processing condition includes a method of processing a waveform of the measurement signal or a type of diffracted light to be used for measurement. Alignment method. 7. calculated using the alignment method according to any one of claims 1 to 6, the sequence information on the static coordinate system of each of the plurality of the processing region on the substrate using An exposure method, wherein a predetermined pattern is transferred onto a substrate that has been aligned. 8. A plurality of regions to be processed regularly arranged on a substrate in accordance with predetermined arrangement information, each of the plurality of regions to be processed being moved with respect to a predetermined processing position in a stationary coordinate system defining a movement position of the substrate. In sequentially aligning, the position information on the stationary coordinate system of at least three pre-selected processing regions among the plurality of processing regions is measured,
By statistically calculating the measured plurality of position information, array information in the stationary coordinate system of each of the plurality of processed regions on the substrate is calculated, and each of the calculated plurality of processed regions is calculated. An apparatus for positioning each of the plurality of processing regions with respect to the processing position by controlling a movement position of the substrate according to the arrangement information, wherein the static coordinates of the at least three preselected processing regions When measuring the position information on the system, by variously changing the signal processing conditions of the measurement signal obtained from the measurement target of the processing area, measuring means for measuring the position information about the processing area, Based on the position information measured for each of the signal processing conditions by the measuring unit and the preset array information, A set of transformation parameters for calculating the sequence information on stop coordinate system,
A first calculating unit that calculates for each of the signal processing conditions; a selecting unit that selects any one set of conversion parameters from the calculated plurality of sets of conversion parameters based on a predetermined condition; A second calculating means for calculating array information on the stationary coordinate system of each of the plurality of processing regions on the substrate using a set of conversion parameters. 9. The predetermined condition includes, for each of the set of parameters, position information on the stationary coordinate system calculated using the conversion parameters, and a position measured under the signal processing conditions. 9. The positioning apparatus according to claim 8, further comprising a residual error component with information, wherein said selecting means selects said set of conversion parameters when said residual error component is minimized. 10. a storage means for storing the signal processing conditions were used with respect to the set of transformation parameters selected in the selecting means, wherein after selection of said set of transformation parameters by the selection means 10. The positioning apparatus according to claim 9, wherein a measurement signal newly measured by the measurement unit is processed under the signal processing condition stored in the storage unit. 11. A position using the array information on the stationary coordinate system of each of the plurality of processing regions on the substrate, which is calculated by the positioning device according to claim 8. An exposure apparatus for transferring a predetermined pattern onto a aligned substrate.